Lake Słupeckie, with an area of over 258 hectares, is an artificial reservoir lake. It was created on the site of a peat bog at the end of 1955, when the area along the post-glacial channel was filled with the dammed waters of the Meszna River flowing from Lake Powidzkie. It is located in the northeastern part of Słupca, in Greater Poland. It is a place for recreation, fishing, and water sports. The island visible from the shore is actually the crown of a rampart of a ring-shaped stronghold from the Lusatian culture. Among the local population, the island is called the Swedish Mound. A legend is associated with it, telling of a trick used by the inhabitants of the stronghold to drive away the Swedes. They allegedly attached burning torches and ringing iron tools to the horns of cows at night. In the prevailing darkness, this created a terrifying effect and caused the invaders to flee in panic. Today, the mound can be viewed from a short distance thanks to a pier with a viewing platform built on Lake Słupeckie.